Improving performance of MLSE in RSOA-based WDM-PON by partial response signaling.

High data-rate upstream transmission in wavelength division multiplexed passive optical network (WDM-PON) based on reflective semiconductor optical amplifier (RSOA) is limited by severe inter-symbol interference (ISI), owing to low-bandwidth transmitter and fiber dispersion. To overcome the limitations in RSOA-based WDM-PON, we propose a novel receiver based on partial response maximum likelihood (PRML) equalization which combines the use of partial response (PR) signaling with maximum likelihood sequence estimation (MLSE). MLSE has been long considered as the optimal reception technique to overcome various types of impairment in optical transmission such as dispersions. It is demonstrated in this paper that PRML surpasses standard MLSE in ISI and reflection suppression with reduced complexity for RSOA-based WDM-PON system. 150 km unidirectional distance is demonstrated for 10 Gb/s uplink, while bidirectional uplinks up to 50 km and 20 km are achieved for data rate of 10 Gb/s and 20 Gb/s respectively, in WDM-PON using PRML. Furthermore, the impacts of discrete reflections on various equalization techniques are investigated, where PRML also shows superiority over MLSE.

Bidirectional optical add-drop multiplexer based on Bragg gratings and circulators.

We propose and demonstrate a bidirectional optical add-drop multiplexer for use in single-fiber bidirectional networks. With effective use of multiport circulators, fiber-Bragg gratings, and a single amplifier element, the new structure can add and/or drop channels in both directions and achieves more than 16 dB of bidirectional gain. The device utilizes Bragg gratings and light absorber to remove Rayleigh backscattered and reflected light at the input stage.